Most well-designed ponds allow for marginal planting, or, if formal, for containers within the pond itself. The sword-like leaves of irises, with their vertical thrust, are especially effective. Best are the forms of Iris laevigata (in shades of blue, purple and white). The white-variegated 'Variegata' is clean and bright - the best variegated iris I know. Its flowers are blue. For yellow, our own native I. pseudacorus does a wonderful job in May-June, but can be embarrassingly vigorous. Here, again, its 'Variegata' variant comes to the rescue. Its glory (though it also flowers) is its pale yellow variegation in spring, which gradually fades to green.

The colour blue is always at a premium. You should include the water forget-me-not, Myosotis scorpioides , the cultivar I grow being 'Mermaid'. These myosotis get going in late spring, but go on and on. The yellow eye is quite a feature. Canadian pickerel weed, Pontederia cordata , does wonders for us in late summer, with arrow-shaped leaves and spikes of blue flowers. It contrasts well with a spear-leaved buttercup, Ranunculus lingua 'Grandiflorus', which has a long season but is extremely vigorous, so watch it.

The skunk cabbage, Lysichiton americanus , seeds itself pretty freely when happy. It is a dramatic plant, with bright yellow arum flowers in March-April, followed by large, lush leaves. No smell to worry about. Arum lilies are a must: their white flowers last for three weeks and have a great presence in the garden from May on. Their glossy leaves are another asset. They will welcome partial shade, but are not out-and-out hardy. I think one should also have the kingcup, or marsh marigold, Caltha palustris , which flowers in quite early spring. In a garden setting, the double 'Plena', packed with glossy yellow petals, gives best value.

The fern to go for is the stately royal Osmunda regalis , which reaches a metre or more when happy. It has an incredibly long season of beauty: bronze fronds unfurl in spring, changing to bright green, which shows up at a distance (if you have seen it wild in Ireland, you'll know what I mean), then to warmest rufous in autumn. Another beauty, among foliage plants, is the undemanding Cyperus vegetus (correctly C. eragrostis ), which is related to the Egyptian papyrus, and has heads of narrow leaves on top of 0.6m naked stems.

Some plants look as though they should be hanging over water, but are actually happiest in normal, well-drained garden soil. This may easily go up to a pond margin and will be a good site for the wand flower or angel's fishing rods, Dierama pulcherrimum . It flowers in high summer, with arching stems carrying little chains of, typically, magenta bells, though the colour varies from quite light pink, intensifying.